void main(List<String> args) {
  //var p1 = Person('12', '24');
  var p = Person.nameAndAge('12', '13');
  p.show();
}

class Person {
  var name;
  var age;
  //dart是没有构造方法重载的
  //Person(this.name, this.age);
  //命名构造函数
  Person.nameAndAge(this.age, this.name);
  show() {
    print(name);
    print(age);
  }

  String toString() {
    return "$name,$age";
  }
}
